Our invention relates to speech analysis systems and, more particularly, to arrangements for word recognition.
Word recognition arrangements permit direct input to communication, data processing and control systems. Such arrangements generally have a reference vocabulary stored as digital templates. A written or spoken input is converted to digital form and compared to the reference templates for identification. It may be difficult, however, to accurately identify the input amongst reference words which are similar. In a reference word vocabulary comprised of, for example, spoken letters of the alphabet, acoustic similarities may impede identification. Letters such as "X, S and F," and "B, C and D" are acoustically confusable and therefore difficult to discriminate accurately.
A prior character recognizer, disclosed in U.S. Pat. No. 4,058,795, issued Nov. 15, 1977 to G. J. Balm, resolves questionable identification of an input character by considering surrounding characters. The surrounding characters are each classified into a group according to a confusability table. The groups are used to determine a context code. The context code is used to select one of the group constituents as the correct identification of the questionable input character. The Balm arrangement assumes that accurately recognized characters surround the questionable character. There are, however, situations in which the identity of adjacent input characters is doubtful. Contextual analysis, as in Balm, may be of limited effectiveness.
In U.S. Pat. No. 4,027,284, issued May 31, 1977 to Hoshino et al, a recognition system for machine printed characters divides a plurality of reference patterns into groups of characters having common pattern elements. Common pattern elements define a standard pattern for each group. The standard pattern which is less than a fixed difference value from an input character is determined. The differences between noncommon pattern elements of characters in the determined group and the input are obtained. The input is identified as the character having the minimum difference value. The Hoshino system may improve recognition accuracy where the number of noncommon pattern elements is fixed, as with machine printed characters. Hoshino may not, however, accurately discriminate between similar characters having a variable pattern of noncommon elements.
It is thus an object of the invention to provide an improved arrangement for identifying an input as one word within a reference vocabulary which includes similar and confusable words.